What's New > Version 2021.03.02

Diffblue Cover CE now available for use on commercial code

Release date: Mar 15, 2021

Diffblue Cover Community Edition now available for use with commercial code

We’ve updated our End-User License Agreement to open up Community Edition for writing tests for both open source and commercial code. This means you can now use Diffblue Cover Community Edition at work completely for free.

Many organisations may have restrictions against using free software or need additional protection. Visit our documentation to learn more about how you can use Diffblue Cover at work.

Writing your first test with Diffblue Cover IntelliJ plugin

Once Diffblue Cover is installed, we’ll index your project (this may take a few minutes).

Once complete, choose any class or method within your Java application, right click and select “Write Tests”.

Diffblue writes your tests under src/test/java for you to review. Every written test is human-readable so that you know exactly what is being tested, and what you need to fix should a test fail. More info is in our documentation.


If you have feedback, questions or requests regarding the Diffblue Cover IntelliJ Plugin, please contact us on the Community Forum. We would love to hear about what is important to you and what you would like to see in upcoming releases.

How do I automatically maintain all of these tests?

Use Diffblue Cover on any CI platform to automatically update your unit tests and catch regressions for every commit - watch this video to learn more.

Full Release Notes


  • IntelliJ Plugin: Cover now provides a notification, with further guidance, when ‘Write Tests’ is selected before Cover has finished indexing the project. [Ref: TG-13942]

  • IntelliJ Plugin: Paid versions of Cover now allow tests to be written for packages by right-clicking the package and selecting ‘Write Tests’. [Ref: TG-13831]

  • Cover’s handling of Maven configurations has been made more robust. To make interactions with Maven easier to debug, additional logging has also been added. [Ref: TG-13799]

Resolved Issues

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, resulted in some tests not being written due to spurious R008 errors. [Ref: TG-14022]

  • Resolved an issue where Cover would incorrectly consider all dependencies in a com package as suitable for test creation. [Ref: TG-13832]

  • Resolved an issue which prevented Cover from adding inner classes in @ContextConfiguration annotations. [Ref: TG-13824]

  • CLI: Resolved an issue where Cover would crash whilst using the --patch-only option when the patch is for a non-Java file. [Ref: TG-13823]

  • Resolved an issue where Cover reported methods in anonymous classes as ‘not considered testable’ with T005 (Trivial constructors are not considered valuable to test). They are now logged as T004 (The method under test is in an anonymous inner class). [Ref: TG-13561]

Known Issues

  • CLI: Windows: creating config.json by outputting --example-config as file causes exceptions. [Ref: TG-11198]

  • CLI: All tests may be discarded in test validation when using --config. [Ref: TG-11475]

  • CLI: dcover clean --working-directory throws an error if --test-output-dir is not provided. [Ref: TG-11665]

  • CLI: Cover fails to generate tests, reporting java.lang.OutOfMemoryError, when analysing projects which spawn a quantity of threads in excess of the operating system’s process thread limit. [Ref: TG-11680]

  • CLI: dcover clean --failing fails when used with a Gradle project. [Ref: TG-11707]

  • IntelliJ Plugin: Diffblue Cover was unable to create an index error may appear if switching project happens before Cover has finished indexing. [Ref: TG-13772]

  • IntelliJ Plugin: Installing a paid version of Cover from disk, without ‘JetBrains Marketplace Licensing Support’ plugin present, results in an inability to write tests. [Ref: TG-13890]